Saturday round-up: Global defrost means less dinner

June 12, 2010 — andyextance

Ice and snow melting from the Himalayan mountains, shown here, feed the Indus and Brahmaputra basins, which are expected to suffer the biggest reduction in food output due to global warming. Credit: Kamaljit S. Bawa

Lower snow and ice reserves in Asian mountains are set to reduce how much water flows into surrounding rivers and can be used to grow food. As a result the rivers will be able to feed around 65 million fewer mouths by 2050 than at the beginning of the century. “Mountains are the water towers of the world,” a Dutch team wrotein leading journal Science on Friday. “Asia’s water towers are threatened by climate change.”

Asia’s five major river basins – the Indus, Ganges, Brahmaputra, Yangtze, and Yellow river basins – provide water to over 1.4 billion people, more than a fifth of the world’s total population. They all contain water from rain and snow that has recently fallen, and melting snow and ice that has collected over a longer timescale. However Dutch companies FutureWater, Deltares and researchers at Utrecht University point out that they don’t all rely on these sources to the same degree. “The effects of climate change on water availability and food security in Asia differ substantially among basins,” wrote the team led by FutureWater‘s Walter Immerzeel.

For example, three-fifths of the water in the Indus Basin in Pakistan comes from melting snow and ice, compared to one-fifth in the Brahmaputra Basin in China, India and Bangladesh and less than one-tenth for the other basins. “There is a general decrease in the ice volumes of Asian basins,” the team writes. Similar reductions in snow and ice volume have been going on since the last ice age, but are expected to speed up due to climate change, thus reducing the amount available to melt and flow into rivers.

After predicted changes in rainfall are taken into account the Brahmaputra basin will therefore be able to feed around 35 million fewer people by 2050, and the Indus basin around 26 million fewer. However, the Yellow river basin should be able to feed around 3 million more thanks to higher rainfall. While Immerzeel and his co-workers point out that these outcomes are less severe than previous studies, they still advise measures be taken to prepare for the scenarios they predict. “We estimate that the food security of 4.5% of the total population [in these areas] will be threatened as a result of reduced water availability,” they write.

Meanwhile, Thursday saw the launch of a report underlining the latest impacts of climate change and other environmental problems on species living in the Arctic. “Sea ice supports of vast array of life in the Arctic and represents a critical habitat for many species,” explain the authors of ‘Arctic Biodiversity Trends 2010’. “Sea ice, however, is being lost at a faster rate than projected by even the most pessimistic of climate change scenarios, such as those reported by the Intergovernmental Panel on Climate Change (IPCC). Early warning signs of losses in the sea-ice food web include declines in populations of some species associated with sea ice, such as ivory gulls and polar bears.”

The report, funded by Canada, Finland, Sweden, Iceland, Norway and the United Nations Environment Program, notes that on land masses in the Arctic, the traditional tundra landscape is gradually being replaced. “The result may be that many of the species that thrive in the Arctic today may not be able to survive there in the future,” it concludes.

Polar bears occur in 19 subpopulations and according to a 2009 review of the status of polar bears, one of the 19 subpopulations appears to be increasing, three are stable, and eight are declining. For the remaining seven subpopulations, there is insufficient or no data to provide an assessment of status and trends. Polar bears are distributed throughout the ice-covered waters of the circumpolar Arctic with an estimated population of 20,000– 25,000 animals. They are fundamentally dependent upon sea ice as a platform for hunting seals, travelling, finding mates, and breeding. Therefore, changes in sea-ice cover and in the patterns of freeze-up and breakup could significantly influence the population of polar bears. Credit: Arctic Council Conservation of Arctic Flora and Fauna (CAFF) Working Group